Alarm circuits



Nov. 8, 1949 v. s. RUTHERFORD ALARM CIRCUITS Filed July 3, 1947 R Rm MRH WT m 8 R O T m V. B

Patented Nov. 8, 1949 ALARM CIRCUITS Victor S. Rutherford, EastCleveland, Ohio, as-

signor to Bailey Meter Company, a, corporation of Delaware ApplicationJuly 3, 1947, Serial No. 758,760

8 Claims.

This invention relates to alarm circuits, and more particularly tocircuits which are sensitive to a variable condition and operate whenthe condition exceeds a predetermined value for giving an alarm.

It is sometimes desirable that there be provided a circuit which isresponsive to a variable condition, such as temperature, and operateswhen the condition goes either above or below a predetermined value togive an alarm. Such a circuit may include, when responsive totemperature, a device subjected to the temperature and operating toaffect the balance of a balanceable network which is desirably energizedfrom a source of alternating current. Output terminals of the networkmay be connected to the grid circuit of a tube having its plate circuitenergized from the source of alternating current used for the network.When the network is unbalanced in one direction, its output voltage isin phase with the voltage applied to the plate circuit, and currentflows in the latter. An unbalance in the opposite direction results inan output voltage which is 180 out of phase with the voltage of theplate circuit, and current flow in the latter is out ofi. A relay may beconnected in the plate circuit and operate to control the flow ofcurrent in a circuit including an alarm, such as a light or bell. Therelay is desirably arranged so that it opens the alarm circuit whencurrent flows in the plate circuit of the tube, and operates to closethe alarm circuit when the current flow in the plate circuit is cut off.With such an arrangement, the alarm circuit is closed with failure ofthe power supply as well as with a change in the condition to a value atwhich the output of the balanceable circuit is out of phase with theplate voltage of the tube. Adjustable means may be provided for varyingthe point at which the temperature responsive device effects a change inthe unbalance of the network from one direction to the other, and meansmay also be provided for reversing the connections of the plate circuitto the source of power so as to reverse its phase with respect to theoutput of the balanceable network, thus varying the direction of changerequired of the condition to bring it to the point at which the alarm isgiven.

An object of my invention is to provide an improved alarm circuit.Another object is to provide an improved circuit responsive to avariable condition and operating when the condition reaches apredetermined value to give an alarm. Still another object is to providean improved circuit including a balanceable network, and

. device.

means controlled by said network and operating on unbalance of thelatter in one direction for giving an alarm. Yet another object is toprovide in an improved circuit, an electron discharge device and abalanceable network energized from a common source of alternatingcurrent and connected together so that the unbalance of the networkregulates the flow of current through'the electron device, a meansresponsive to a condition and controlling the unbalance of the network,and an alarm circuit controlled by the current flow through the electrondischarge Other objects will appear in the course of the followingdescription.

In the accompanying drawing there is shown for purposes of illustration,one form which my invention may assume in practice; the single figurebeing a schematic diagram of my improved circuit adapted to give analarm when the temperature of the furnace reaches a predetermined value.

As shown in the drawing, my improved circuit, generally designated i, isresponsive to the temperature within a furnace 2, and operates at apredetermined temperature to give an alarm, as by completing a circuitincluding a lamp or a bell 3. The circuit I, as shown, comprises abridge 5 having impedance windings 6 and l of reactor converters A and Bforming one pair of its legs, and fixed resistances 8 and 9 forming theother pair of legs. Input windings II and I2 of the converters areconnected in series in a circuit including a thermocouple l4 and apotentiometer IS. The thermocouple is subjected to the temperatureproduced in the furnace by the burning of fuel supplied through aconduit l8, and the potentiometer is subjected to a constant D. C.voltage, as by a battery ll or a regulated D. C. supply. One terminal ofthe thermocouple is connected by a conductor 18 to one end of the inputwinding l2, while the other terminal of the thermocouple is connected byconductors 20, 21, a variable portion of the potentiometer, anadjustable potentiometer contact 22, and a conductor 23 to one end ofthe input winding II. The connection between th thermocouple and thepotentiometer is such that the voltage drop across the portion of thepotentiometer included in the circuit with the input windings opposesthe voltage of the thermocouple in determining the flow of currentthrough the circuit. Bias windings 25 and 26 of the reactor convertersare connected in series across the battery I! in such a way that oneopposes one of the input windings while the other aids the other inputwinding in determining the reactance of the impedance windings 6 and 1.

The diagonally opposite points of the bridge between the pairs of legsare connected by conductors 28 and 29 to the secondary winding of atransformer which has its primary winding connected by conductors 3| and32 to a source of alternating current. The diagonally opposite ointsbetween the legs of each pair are connected by conductors 34 and 35 tothe grid 36 and the cathode 31 of a tube 38. As disclosed more fully inan application by A. J. Hornfeck, Serial Number 453,486, filed Auust 3,1942, the reactor converters operate in the bridge circuit to change alow level direct current signal of given polarity to a greatly amplifiedalternating current signal of given phase, and to reverse the phase ofthe alternating current signal 180 when the polarity of the directcurrent signal is reversed. The amplified A.-C. signal is applied by theconductors 34, 35 to the tube to establish a voltage diiierence betweenthe grid 36 and the cathode 31. The cathode and an anode 39 of the tubeare connected by conductors 40 and 4| to a reversing switch 42 which isadapted to connect them in one direction or another to the conductors3|, 32 leading to the source of A.-C. Connected in the circuit in serieswith the anode is a winding 44 of a relay having its armature 45connected to a contact arm 46 pivotally supported at 41 and adapted toengage a contact 48 or acontact 49. A spring 50 tends to hold thecontact arm in engagement with the contact 49, and the relay operateswhen energized to move the contact arm into engagement with the contact48. A conductor 52 connects the contact 49 to one terminalof the hell 3,and a conductor 54 connects the other terminal of the bell through abattery 55 to the contact arm.

When the bridge output voltage applied to the grid of the tube is inphase with the anode or plate voltage applied by the power source to thetube through the conductors 40, 4|, current will flow through the platecircuit including the winding 44 of the relay, and the contact arm 46will be moved by the relay into engagement with the contact 48. As soonas the bridge output becomes out of phase with the plate voltage, theflow of current through the plate circuit is cut off, and the contactarm is moved by the spring 50 into engagement with the contact 49,completing the circuit through the bell to give an alarm. The point atwhich the output of the bridge changes from one phase to the other isdetermined by the adjustment of the potentiometer contact 22. As long asthe voltage drop across the portion of the potentiometer connected inseries with the thermocouple exceeds the voltage of the latter, thebridge is unbalanced in one direction, but as soon as the thermocouplevoltage exceeds the voltage drop across this portion of thepotentiometer, the bridge is unbalanced in the opposite direction.

If it is desired that the alarm be sounded when the furnace temperaturegoes above the value at which the direction of bridge unbalance changes,then the reversing switch 42 is moved to the position at which the platevoltage is in phase with the output of the bridge when the temperatureis low. An increase in the temperature to a value at which the output ofthe bridge reverses in phase results in a grid voltage which is out ofphase with the plate voltage. The flow of current in the plate circuitis then cut ofi and the contact arm 45 is moved by the spring tocomplete the alarm circuit.

To cause the alarm circuit to be completed when the temperature dropsbelow a predetermined value, it is only necessary to position thereversing switch 42 so that the plate voltage is in phase with the gridvoltage when the temperature is above the predetermined value. It willbe appreciated that the controls for the contact arm 46 as describedwill operate on failure in the' power supply or of any part of thesystem to complete the alarm circuit.

While there is described in this application one form which my inventionmay assume in practice, it will be understood that it may be modifiedand embodied in various other forms without departing from the spirit orthe scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A system for giving an alarm upon changes in a condition in onedirection beyond a predetermined value comprising, in combination, abalanceable network, means for energizing said network from a source ofalternating current, said network operating to produce an alternatingcur rent output voltage of one phase on unbalance in one direction andof opposite phase on unbalance in the opposite direction, meanssensitive to the condition and operating to unbalance said network inone direction or the other as the condition goes above or below thepredetermined value, an electron discharge device having an anode, acathode and a grid, means for energizing said grid by the output of saidnetwork, a circuit for energizing said anode from said source of A.-C.,an alarm circuit having a c0nta0tor movable to open and closedpositions, means for urging said contactor to one of said positions, anda relay having a winding connected in said first mentioned circuit andan armature connected to said contactor, said armature operating whensaid winding is energized to move said contactor to the other of saidpositions.

2. The system of claim 1 in which a reversible switch is connected insaid anode circuit for reversing the connections of the latter to saidsource of A.-C., the position of said reversing switch determining thedirection of unbalance necessary to give an alarm.

3. A system for giving an alarm upon changes in a temperature in onedirection beyond a predetermined value comprising, in combination, aWheatstone bridge having a pair of balanced impedance arms, a secondpair of arms each comprising an impedance winding of a saturable corereactor, each saturable core reactor having a bias winding and an inputwinding, a, thermocouple-potentiometer system having a thermocouplesubjected to the temperature and a slidewire subjected to the voltage ofa battery, means for connecting the output of saidthermocouplepotentiometer system to said input windings, means tofixedly energize said bias winding, means for energizing one conjugateof said bridge from a source of alternating current, a thermionic tubehaving a grid circuit and a plate circuit, means for connecting theother mentioned bridge conjugate to said grid circuit, means forconnecting said plate circuit to said source of A.-C., said lastmentioned means including a winding of a relay, an alarm circuitincluding an alarm device, a battery, and a contactor adapted to bemoved to open or closed positions, and means for connecting an armatureof said relay to said contactor for positioning the latter,

4. A system for giving an alarm upon a change in a variable in onedirection beyond a predetermined value comprising, in combination, meansresponsive to the variable ior establishing an alternating currentpotential of a phase varying relative to the phase of a source of A.-C.in accordance with the direction in change of the variable from saidpredetermined value, a thermion c tube having a, grid directly energizedfrom scil A.-C. potential and a plate energized from said source, arelay having a winding connected for energization with said plate, analarm circuit, and means connected to said relay for controlling saidalarm circuit.

5. A system for giving an alarm upon a change in a variable beyond apredetermined value comprising, in.combination, means responsive to thevariable for establishing an alternating current potential of a phasevarying relative to the phase of a source of alternating current inaccordance with the direction in change of the variable from saidpredetermined value, a thermionic tube havin a, grid and a plate, meansfor energizing said grid directly from said A.-C. potential, a, circuitfor connecting said plate to said source of A.-C., an alarm circuithaving a contactor adapted to be moved to open and closed positions, anda relay having a winding included in said plate connecting circuit andan armature connected to said contactor.

6. The system of claim 5 in which said plate connecting circuit includesa switch adapted to be positioned manually for reversing the connectionof said plate to the source of A.-C., and said relay operates whenenergized to move said contactor to its open position.

'7. A system for giving an alarm upon changes in a condition in onedirection beyond a predetermined value comprising, in combination, aWheatstone bridge having a pair of balanced impedance arms, a secondpair of arms each comprising an impedance winding of a saturable corereactor, each saturable core reactor havin a bias winding and an inputwinding, a circuit including a device responsive to said condition andoperating to energize said input windings, means for fixedly energizingsaid bias windings, means for connecting said bridge at points betweensaid pairs of arms to a source of alternating current, a thermionic tubehaving a grid circuit and a plate circuit, means for connecting saidgrid circuit to said bridge at points between the arms of said pairs,means for connecting said plate circuit to said source of A.-C., saidlast mentioned means includin a winding of a relay, an alarm circuithaving a contactor adapted to be moved to open and closed positions, andmeans for connecting an armature of said relay to said contactor forpositioning the latter.

8. The system of claim 7 in which said means for connecting said platecircuit to said source of A.-C. includes a switch adapted to bepositioned manually for reversing the connection of said plate to theA.-C. source.

, VICTOR S. RUTHERFORD.

REFERENCES CITED UNITED STATES PATENTS Name Date Jones Oct. 21, 1947Number

